Roof drill bits having a round head with extending prongs in opposite quadrants of the bit are illustrated in a U.S. Pat. No. 4,165,790, to Emmerich, issued Aug. 28, 1979. The opposed prongs are in opposite sides of a diameter of the bit and support a cutting blade diametrically-positioned in recesses provided in the ends of the prong. A driving means on the head opposite the blade mechanically interfits with a drive steel rotated by a suitable power unit. In Emmerich U.S. Pat. No. 4,190,128 (Feb. 26, 1978), a similar type of bit is disclosed but the claimed improvement in this bit is a body with a polygonal configuration in cross-section which will blend with a similar configuration (usually hexagonal) on a driving steel. The driving surface on the bit can be a shank with an ensmalled male portion to interfit with a drill steel or a shank with a hexagonal female recess to interfit with a male hexagonal driving projection in a drill steel.
It is an object of the present invention to provide a drill steel design which greatly improves the drilling efficiency of the bit and provides a greater drilling speed in comparison with previous bits.
It will be appreciated that these bits are used with either a vacuum system or a pressure system through the passages in the bits and driving steels to assist in the removal of the cuttings and dust resulting from the drilling operation. The vacuum system is most common in many operations.
An example of a suction type bit is found in a patent issued to O'Connell, U.S. Pat. No. 4,313,506 (Feb. 2, 1982) where there is disclosed a round drill bit with a cross blade above suction openings leading into a driving shank having a central passage which receives a hollow drive steel having a driving engagement with a female recess in the bottom of the shank.
The present disclosure is directed to a bit similar to that shown in U.S. Pat. No. 4,190,128, above referenced, for use in a suction type system. The bit is preferably a polygonal outer surface which will register with a similar polygonal surface on a drive shank (drill steel) but the features of the present invention may also be incorporated in a bit having a round outer surface.
One essential feature of the bit of the present invention is an enlarged cutting hole in the wall of the bit. The hollow center of the bit is connected to the empty quadrants of the cutting end of the bit through holes in the wall of the bit which extend through a large angle of the circumference. At one instance the port extends essentially from a diameter of the bit to a chord which is perpendicular to the reference diameter and spaced to the other side of the center of the bit a distance substantially equal to the total width of the cutting insert at the end of the bit. The bit may be manufactured as a casting or as a forging, with some machining operations if required.
This construction has proven to be extremely effective in removing the cuttings and powder while increasing the drill rate materially.
Objects and features of the invention will be apparent in the following description and claims in which the invention is described together with details to enable those skilled in the art to practice the invention, all in connection with the best mode presently contemplated for the invention.